<%@ page language="java" pageEncoding ="UTF-8"%>
<html>
	<head>
		<title>Ajax应用</title>
	</head>
	<script type="text/javascript">
		var xmlHttp;
		function createHttpRequest(){
			if(window.ActiveXObject){
				xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
			}else if(window.XMLHttpRequest){
				xmlHttp=new XMLHttpRequest();
			}
		}
		function beginCheck(){
			var xh=document.all.xh.value;
			if(xh==""){
				alert("对不起，请输入注册学号！");
				return;
			}
			createHttpRequest();
			xmlHttp.onreadystatechange=processor;
			xmlHttp.open("get","CheckUser?xh="+xh);
			xmlHttp.send(null);
		}
		function processor(){
			var responseContext;
			if(xmlHttp.readyState==4){
				if(xmlHttp.status==200){
					responseContext=xmlHttp.responseText;
					if(responseContext.indexOf("true")!=-1){
						alert("恭喜你，该学号有效！");
					}else{
						alert("对不起，该学号已经被注册！");
					}
				}
			}
		} 
	</script>
	<body>
		<form action="">
			学号：
			<input type="text" name="xh" onchange="beginCheck()"/>
			口令：
			<input type="password" name="kl"/>
			<input type="submit" value="注册"/>
		</form>
	</body>
</html>